networking: add new budget_interval field to retry budget traffic policy

networking/v1alpha3/destination_rule.proto

@@ -303,6 +303,21 @@ message TrafficPolicy {
     // Defaults to 3.
     //
     uint32 min_retry_concurrency = 2;
+    // Specifies the duration in which requests will be considered when calculating
+    // the budget for retries. This parameter alters the way in which the retry budget
+    // is calculated, overriding the default behavior when specified.
+    //
+    // By default, when budget_interval is set to 0ms, only presently active
+    // and pending requests are considered when calculating the retry budget.
+    //
+    // When a non-zero budget_interval is specified, new requests are
+    // considered for the duration of budget_interval when calculating
+    // the retry budget.
+    //
+    // Defaults to 0ms.
+    //
+    // +protoc-gen-crd:duration-validation:none
+    google.protobuf.Duration budget_interval = 3;
   }
 
   // Specifies a limit on concurrent retries in relation to the number of active requests.

releasenotes/notes/60389.yaml

@@ -0,0 +1,11 @@
+apiVersion: release-notes/v2
+kind: feature
+area: traffic-management
+issue:
+  - https://github.com/istio/istio/issues/60389
+releaseNotes:
+  - |
+    **Added** `budget_interval` field to the RetryBudget TrafficPolicy API to
+    configure the interval with which requests are considered when calculating
+    the retry budget. The default value, 0ms, retains the existing behavior of
+    considered only in-flight requests.